The proposed research will investigate the effects of residential and educational environments on four sets of outcome variables as they relate to the mentally retarded: (a) mortality and the development of adaptive behavior, (b) personal-social development, (c) cognitive development, and (d) school and home adaptation. The research is based on rigorous investigation of the impact of two powerful and pervasive forces in the provision of services for mentally retarded persons - the principles of normalization and mainstreaming. In addition, the longitudinal study of mortality and changes in adaptive behavior for a five- to ten-year period is suggested to discern developmental trends on a large population of mentally retarded individuals from a number of states. Four interrelated projects are proposed, each of which has its own specific aims, methods of procedure, and significance. All of them relate to the basic model, and all have as their ultimate objective the discovery of ways to improve retarded individuals' adaptation to their environments.